While looking into this series, I realized that Davids patch commit acd05785e48c01edb2c4f4d014d28478b5f19fb5 Author: David Matlack <dmatlack@xxxxxxxxxx> AuthorDate: Fri Apr 17 15:14:46 2020 -0700 Commit: Paolo Bonzini <pbonzini@xxxxxxxxxx> CommitDate: Fri Apr 24 12:53:17 2020 -0400 kvm: add capability for halt polling broke the possibility for an admin to disable halt polling for already running KVM guests. In past times doing echo 0 > /sys/module/kvm/parameters/halt_poll_ns stopped polling system wide. Now all KVM guests will use the halt_poll_ns value that was active during startup - even those that do not use KVM_CAP_HALT_POLL. I guess this was not intended?